1. Field of the Invention
The present invention relates to a method and a controller for identifying a drag gesture and particularly to a method and a controller for identifying a drag gesture on a touch device and generating a drag signal, which simulates an object dragged by a mouse.
2. Description of Related Art
The graphical user interface (GUI) is a program operational interface developed by ZEROX PARC research center and the GUI is used in company with a pointing device such as a mouse. The user only needs to move the mouse with a visional type pointer and make a click then a desired action can be performed easily so as to solve the problem of inconvenience resulting from the text mode being required to input complicated instructions. Hence, the GUI was adopted by Apple computer company and Microsoft company one after another to become the most popular mode in all the operational systems. The pointing device has become a basic outfit in electronic equipment applying the GUI such as desktop computer, notebook computer, flat panel computer and personal digital assistance (PDA).
Currently, the pointing device includes external mouse and a track ball touch pad built in a portable computer system and a touch panel joined to the screen. The mouse is the earliest developed pointing device. Taking the mouse as an example for explaining the function of pointing device, the mouse can control the pointer on the screen of the electronic device, that is, where the mouse is moved, where the pointer is moved. Then, an execution instruction to the electronic device can be carried out by way of pressing the control button on the screen for a target ready to be executed. Nevertheless, design with lightness, smallness, shortness and thinness is a trend of electronic equipment and, for instance, the laptop computer is getting to replace the desktop computer so that the small sized touch device such as the touch panel is getting a main stream pointing device gradually.
The technique of current touch pad mainly includes capacitance type, resistance type, electromagnetic type, pressure type, inductance type, surface sound wave type and optical type. When a object body such as a finger moves on the touch pad, the pointer can be controlled to move along direction of the object body. Further, the pointer needs to have a function of carry out an order in addition to controlling movement of the pointer. Taking operating the mouse as an example, when the pointer moves to an object ready to be moved such as a program, a document or a picture, one of the buttons on the mouse such as the left button can be kept pressing in company with moving the mouse. In this way, the object can be dragged to other places. As for the touch device such as the touch pad, mostly there are two control buttons provided additionally instead of the left and right buttons on the mouse or the object body is defined to make a certain gesture on the touch device such that signals resulting from continuing pressing a button of the mouse can be generated along with the object being moved and dragged to other places.
An ordinary touch device usually simulates a drag movement of mouse with a drag gesture and the way to carry out the drag gesture is to implement a tap and a displacement following the tap immediately so as to let the object moving. Hence, U.S. Pat. No. 6,414,671 has disclosed a method for identifying a drag gesture on the touch device. With reference to FIG. 1, when a time duration t4 of the object body appearance at the first time (i.e. stay time of the object body appearing on the touch device at the first time) is compared to the first reference time value, a drag signal 11 generates in case of the time duration t4 being less than a first reference time value. Then, a time span t5 between the first time appearance and the second time appearance is compared to a second reference time value and the drag signal 11 is kept and X, Y information generates repeatedly within the time duration t5 at the second time in case of the time span t5 being less than the second reference time value.
Although the conventional method can achieve the purpose of identifying the drag gesture, the time duration t4 of first appearance and the time span t5 between the first appearance and the second appearance being compared to a respective reference time value corresponding to them makes determination complicated. Also, X, Y information being generated repeatedly within the time duration t6 of the second appearance results in more complicated design. Further, due to personal differences between users, time for various stages of movement done by each person during performing the drag gesture may be different from each other. Even the same person may have different time durations for movements while the drag gesture is performed at different times. Hence, it is easy for the conventional method to occur misjudgment. In addition, it is easy for the touch device to be touched accidentally during operation or to occur phenomena of temporary spike of the first appearance, temporary spike time span between the first appearance and the second appearance and temporary spike of second appearance due to the touch device generating noise at work or being caused by interference of foreign noise. The conventional method does not have a minimum time limitation to the time duration of first appearance, the time duration of second appearance and the time span between the first appearance and the second appearance so that it is easy to occur incorrect determination to the signal generated due to the noise interference.